In recent years, energy saving has been given importance, and also in a liquid crystal display device (Liquid Crystal Display) having a liquid crystal panel, reduction in power consumption has been an important theme.
Furthermore, a commercial product using a light source of a light-emitting diode (LED) as a backlight in a liquid crystal display device has been sold.
A light emission luminance adjustment system of the LED backlight includes a Pulse Width Modulation (PWM) system and a current value control system. Since the PWM system is for performing time control, control thereby is highly accurate and fine control is able to be performed. On the other hand, the current value control system is higher in power efficiency than the PWM system, however, is not suitable for fine control, thereby performs stepwise control since a control width is not able to be finer as the PWM system, and correction is needed in the case of performing linear control.
Patent document 1 discloses a liquid crystal display device provided with a backlight driving portion for supplying R, G and B driving currents and R, G and B PWM signals to an LED backlight portion and for controlling light emission luminance and chromaticity of each of R, G and B backlights, and a timing controller for controlling an operation of a scan driver, a source driver and the backlight driving portion.